1. Field of the Invention
The present invention relates to a motion-detecting module, and particularly relates to a motion-detecting module for combining a light-emitting function and a light-sensing function together.
2. Description of the Related Art
FIG. 1 shows a cross-sectional, schematic view of an image-sensing device of the prior art. The image-sensing device of the prior art includes a main PCB la, a light-emitting element 2, an illuminant-fixing mechanism 3, an image-sensing element 4a, and a package casing 5a. 
The light-emitting element 2 is fixed on the illuminant-fixing mechanism 3 and is electrically connected with the main PCB 1a via a leading wire 20. Moreover, the image-sensing element 4a is disposed on the main PCB 1a and is electrically connected with the main PCB 1a via a plurality of leading wire 40a. Furthermore, the package casing 5a is cover on the image-sensing element 4a and has an opening hole 50a for exposing the image-sensing element 4a. Therefore, the light-emitting element 2 generates a beam B1 onto a surface S to form a reflected beam B2, and the reflected beam B2 is projected onto the image-sensing element 4a through the opening hole 50a for sensing the image of the surface S.
However, the light-emitting element 2 and the image-sensing element 4a are separated from each other. The relationship between the light-emitting element 2 and the image-sensing element 4a needs to be adjusted accurately, so that the image-sensing element 4a can accurately sense the reflected beam B2. Hence, the prior art leads to a complex manufacturing process with large tolerances. Besides, the illuminant-fixing mechanism 3 and the package casing 5a are separated from each other, so that the manufacturing cost of the prior art is high.
In other words, it is difficult to precisely position the light-emitting element 2 and the image-sensing element 4a on the main PCB 1a, and alternatively, a light-guiding device (not shown) for the image-sensing device has a large assembling tolerance, so that the judgment capability of the image-sensing device would be affected.